1. Field
The following description relates to a network technology, and more particularly, to a technology for supporting multicast handover for a mobile node.
2. Description of the Related Art
Unicasting transmits data to a single receiver, whereas broadcasting transmits data to all receivers in a network. In contrary, multicasting transmits data to a specific group of receivers in the network. In IP multicasting, in response to a single data packet transmitted from a multicast source, the data packet is replicated as many as the number of receivers that are willing to receive a corresponding source in a network and the replicated packets are delivered to the receivers. Thus, less overhead is incurred to the source which requires transmitting a replicated packet as many times as the number of the receivers and bandwidth can be saved since less number of packets are transmitted over the network, compared to the other transmission schemes.
Various application services based on multicast have been provided. With the fast development of mobile terminals including smart phones, a range of targets of the multicast services has varied from fixed hosts to mobile hosts. A mobile host moves from one network to another or from one cell to another in the same network. Hence, a multicast technology for a fixed host additionally requires a technique to process fast and consecutive multicast traffics in a handover situation.
In the multicast processing technique, traffic process is performed independently in layer 3 and layer 2 due to a network structure for a multicast service. For example, in layer 3 (a router level), traffic process is performed by layer 3 network equipment using multicasting routing protocol based on Internet group management protocol (IGMP) or multicast listener discovery (MLD) protocol which is produced by a mobile host. On the other hand, in layer 2, multicast traffic is processed or broadcasted using IGMP snooping scheme.
However, in the case of broadcasting process, efficient use of network resources is difficult.
The IGMP snooping scheme may be dependent on an IGMP message transmitted between the mobile host and a router. In a case where a mobile host moves from one cell to another in use of a multicast service, if the mobile host in a new cell does not generate an IGMP message, it is not possible for an access point (AP) of the new cell and upper layer 2 network equipment to learn that the mobile host is using the multicast service. This may result in stopping the multicast service from being provided to a mobile host user.
To use the multicast service, multicast group membership protocol is necessarily used. Examples of the multicast group membership protocol may include IGMP and MLD protocol.
The IGMP/MLD protocol is signaling protocol for managing multicast groups in an effort to facilitate the indication of multicast groups which include a router and various hosts which form a sub-network. The IGMP protocol may be used in an IPv4 environment, the MLD protocol is used in an IPv6 environment. IGMP/MLD protocol is developed on the basis of a weird network environment. Thus, for a multicast service in a wireless network environment, a modified IGMP/MLD protocol has been actively researched and developed in consideration of the wireless mobile network environment.
The most influential factor for stability and performance of a multicast service in a wireless mobile environment is a wireless section. In a wireless section, resources are very limited, and the data transfer speed is much slower than in a wired section. The limited conditions of the wireless section may cause loss of IGMP/MLD protocol messages between a mobile host and a router for use of the multicast service. For example, such loss of messages may take place during handover while moving images in a multicast scheme is being provided to a mobile host user. Because such handover happens while the user is viewing the moving images in a multicast scheme, the user may consider the handover as more serious than any other events.
Even when no loss of IGMP/MLD protocol messages occurs during handover, handover delay time of multicast traffic is elongated due to a slow data transfer speed in a wireless section. This may cause unsmooth display of the moving images while the user is viewing them.